Photographic emulsion



June 7, 1932. L. G. s. BROOKER 1,861,836

PHOTOGRAPHIC EMULSION Filed March 19, 1930 Fig.2.

-Lealie (i. 5. Breaker.

Patented June 7, 1932 UN-ETED STATES PATENT GFFICE LESLIE G. S. BROOKER,F ROCHESTER, NEW YORK, ASSIGNOE. TO EASTMAN KODAK COMPANY, OFRQCIIEfiTER, NEW YORK, A CORPORATION OF NEW YORK PHOTOGBAPHIC EMULSIONApplication filed March 19, 1930. Serial No. 437,017.

This invention relates to a new composition of matter and particularlyto a new class of photographic sensitizing dyes and methods for theirpreparation.

It is well known in the photographic art, that in order to renderphotographic emulsions sensitive to substantially all the visible raysof the spectrum, it is necessary to treat the emulsion,, either byovercoating or by admixture with the emulsion itself, with a compoundwhich extends the sensitivity of the emulsion beyond its naturalsensitivity. An untreated emulsion will generally record only the shortwaves, such as the blue and violet. By the proper use of a suitable dye,this restricted sensitivity can be varied at will within certain limits;for example, the emulsion can be rendered strongly sensitive to green orblue or to any of the other visible bands of the spectrum, or it can berendered sensitive to all the visible rays in substantially equaldegrees.

The object of the present invention is to provide a light sensitiveemulsion, the sensitivity of which is augmented over certain bands ofthe spectrum. Another object of this invention is to provide a lightsensitive dye to be incorporated in or coated upon, photographicgelatino silver halide emul sions in order to increase their colorsensitivity. A further object of this invention is to provide a methodfor the preparation of such dyes. Other objects will hereinafter appear.

I have found that cyanine dyes and particularly the thio-iso-cyaninesand the thiopseudoscyanines, the latter being sometimes calledthio-ip-cyanines, which have been preparedfrom mu methylnaphthothiazole, as well as the S-methyland naphthalene substitutedthiocarbocyanines, either substituted or unsubstituted, representclasses of dyes which are excellent photo-sensitizers. These dyes, whenprepared in the manner described herein, together with the substitutionproducts of these dyes, are especially useful for addition directly tothe gelatino-silver-halide emulsion, which may be coated on plates,films or other materials. Furthermore, these dyes are useful asovercoatings for photographic light sensitive surfaces, thereby increasing the light sensitivity of that surface.

In the accompanying drawing the color sensitivity of test emulsions, inwhich members of the class of dyes were incorporated, are shown.

Figure 1 is a reproduction of a plate coated with an emulsion containing1 2 diethyl- 3:a-benzothio-iso-cyanine iodide which was exposed in aspectro sensitometer. The abseissae are graduated in micromillimeters(,a while the ordinates are graduated in divisions denoting a decreasingintensity of the light rays as they affect the emulsion, the greatestintensity of any wave being at the base line. Below the stippled areacomplete maximum density is indicated with no appreciable reduced silverat the upper boundary of the stippled area. A gradual gradation inintensity extends through this area. The emulsion, of course, is fullyreduced below the stippling. It will be noted from this chart that thisdye renders the photographic emulsion highly sensitive at a wave lengthof 560 an and from there on extending well into the yellow, itssensitivity ending at little beyond 600 It will likewise be noted thatthere is unusually good strength through the green.

Figure 2 is a. drawing of a similar chart resulting from the exposure ofa plate coated with 1'12 diethyl 3 4L benZothio-pseudo-cyanine iodide.This dye gives a sharp maximum at 560 pa with a fair strength in thegreen, the sensitivity extending to about 610 ,a The emulsion, as wasstated above, is responsible for the greater part of the sensitivity inthe blue and violet 3905OO IL/1.-

I will now explain a method for the proproduction of this particularclass of dyes, but it Will be understood that I am not to be restrictedby the definite proportions or exact ingredients therein given except asthey may be so indicated by the claims appended hereto. It will likewisebe understood that the chemical structural formulae employed herein aretheoretical and are given so that those skilled in the art may morereadily understand the composition. of these dyes. Whether or not thechemical structure given is correct will in no way limit the scope ofthis invention as the methods for the preparation of the dyes, togetherwith the suggested equivalents that may be used in such preparationswill enable the skilled organic chemist to prepare these dyes, whatevertheir theoretical struc tural formulae may be.

The structural formulae given, however, are believed to be correctaccording to present knowledge.

Shep A 1 methyl alpha naphthothiazole Crude The reaction may beconducted in two steps. Step A One molecular proportion of l-methylalpha naphthothiazole is condensed with one molecular proportion ofethyl-ptoluene sulfonate by heating the substances separates and may berecrystallized from methyl alcohol. The resulting dye obtained consistsof scarlet needles which impart to a methyl alcohol solution a crimsonred coloration. The several reactions are believed to be as follows:

0 3 naphthothiazole ethy1-p-toluene etho-p-toluene sulfonate sulfonateNOSO2 Ema/mph: J.In the preparation of 1' 2- diethyl-56-benzothio-iso-cyanine iodide, one member of the series, I firstprepare from beta-naphthylamine the intermediate 1-methyl alphanaphthothiazolo by Well known academic methods. This intermediate hasthe following structural formula:

S DiCCHa 7 8 The isomeric 2 methyl beta naphthothiazole has thefollowingstructure:

Example 2.If an'equivalent amount of 2-methyl-beta-naphthothiazoleethiodide be used in place of the 1-methyl-alpha-naphthothiazole ethop-toluene sulfonate used in EX- ample 1, a product will be obtainedconsisting of brown needles with a. brassy green reflex. This dye willgive a crimson solution in methyl alcohol. This may be called 1 2-diethyl-8 4-benzothio-iso-cyanine iodide.

Eammple 3.In the preparation of 1 z 2 diethyl 3i-benzothio-pseudo-cyanine iodide, another member of the series, I firstprepare a 2 methyl-beta-naphthothiazole ethiodide by the followingmethod:

Equimo-lecular proportions of Q-methyl-B- naphthothiazole and ofethyl-p-toluene sulfonate are heated. together in an oil bath for a weekat 130140. WVhen this salt is to be used it is purified by extractingthe unchanged starting materials with acetone, in

which the 2-methyl-,8-naphthothiazole ethop-toluene sulfonate issparingly soluble. This salt may be converted into the iodide by doubledecomposition in fairly concentrated aqueous solutions with potassiumiodide, whereby 2methyl-,B-naphthothiazole ethiodide is obtained. Thissubstance is washedand dried at an elevated temperature, and has thefollowing composition:

The dye may be made from this intermediate in one step: 9.5 parts of2-methyl-B- naphthothiazole ethiodide and 11 parts of 2- iodo-quinolineethiodide are suspended in 63 parts of absolute ethyl acohol. To thissuspension are added with constant vigorous shaking 3.6 parts ofpotassium hydroxide (of about purity) in absolute ethyl alcohol, thealkali being added to the boiling alcoholic suspension gradually duringa period of from 5 to 10 minutes. Boiling is con tinued for a period of15 minutes after all the alkali has been added. The dye is filtered fromthe cooled solution and is purified by washing with boiling water andthen with cold water followed by acetone. If the above example beconducted by using parts by weight in the c. g. s. system a yield ofapproximately 8.9 grams of unrecrystallized dye will be produced. Thisis purified by crystallization from methyl alcohol and is obtained inlight brown plates and gives to of triethyl ortho acetate for 1 hours.An excess of ammonium bromide in hot water is added and the wholeallowed to cool. Crystals of 8-methyl-2:2'-diethyl-3:4: 3z4 dibenzothiocarbcyanine bromide are thereby obtained.

Ewample 6.One part of l-methyl-alphanaphthothiazole is heated with onepart of allyl iodide'under reflux on a steam bath. The initial reactionis rapid and heating is continued for a further 2 hours. The product isdissolved in 19 parts of pyridine and boiled under reflux with 1.5 partsof ethyl ortho formate. 2:2 diallyl 5:6:526 dibenzo thiocarbocyanineiodide is obtained after precipitation with potassium iodide.

The nomenclature and the numbering of these compounds and intermediatesare the same as that used in my co-pending application, Serial Number337,177 filed February 2, 1929. This numbering, of course, is entirelyarbitrary but the system herein employed is according to current usage.A thio iso cyanine dye derived from l-methylalpha-11aphthothiazole, forinstance, will have the following structure:

and will be called a l 2-dialkyl-5: 6-benzo thio-iso-cyanine salt.

s s\ OCH; 2KOH 0:011 2H2O 2K1 t p0 asslum I /N\ hydroxide f /N\ zHn I02H I (hHn 02H I 2-iodo-quinoline ethiodide Z-methyl-B-naphtho- 1 :2dlethyl thiazole ethiodide 3:4 benzo thlo-pseudw.

cyanine iodide Example {tr-It in the above reaction (Example a1-methyl-alpha-naphthothiazole ethiodide is used in place of the2-methyl-B- naphthothiazole ethiodide there is obtained a 1 2-diethyl-56-benzothio pseudo-cyanine iodide. This dye crystallizes in light browncrystals which, on solution in methyl alcohol, give to that solution apinkish orange coloration.

. flux in 24 parts of dry pyridine with 8.1 parts rived from the2-methyl-B-1iaphthothiazole will have the following structure:

and in accordance with the numbering system used w th the above dye,dyes of thisv class A dye similarly der the bases are drawn as shown.

will be called 1:2-dialkyl-3:4-benzo=thioiso-cyanine salts.

A thio pseudo cyanine dye derived from l niethyl-alpha-naphthothiazolealkyl quaternary salt, for instance, will have the following structure:u

and will be called a lz2-dialkyl 5:.6-bcnzo thio-pseudocyanine salt. 7V.

A thio pseudo cyanine dye derived from 2-methyl-B-naphthothiazole alkylquaternary salt will have the following structure:

and in accordance with the numberingsystem used will be al'zQ-dialkyl3:4-benzo thiopseudo-cyanine salt. I

It will be noted that of the two intermediates specifically disclosed,one is called the 2-methyl-beta, the other the 1-methyl-alphanaphthothiazole. This nomenclature, while it appears somewhatinconsistent, is that in current usage, and results from a numbering ofthe rings counter clockwise for the. 2- methyl-beta and clockwise forthe 1-1nethylalpha naphthothiazole when the structures of calling theml-methyl or 2-methyl, the intermediate carbon atom to which the methylgroup is attached being the same in either case, this position issometimes called the mu position. When mu appears herein, therefore, itwill refer to this intermediate carbon atom.

By a substitution in the above major structural formulae of similar ordissimilar alkyl radicals in the R positions many sensitizing dyes maybe obtained. The X indicates any Instead of come within the scope ofthis invention as will also dyes containing substituents in thequinoline nucleus. 7

In the preparation of an emulsion containing these photo-sensitizers, ithas been found that they may be incorporated from their solution inmethyl alcohol in from 5 to 100 milligrams to 100 cc. ofthe emulsion.l/Vhile some of the sensitizers require less, others require more thanthe amounts given above, generally about milligrams is sufficient toobtain the maximum sensitivity efiect from a dye having good sensitizingpower. The more powerful dyes, however, may require as little as 5milligrams.

It is apparent from the above description that any of the thio-iso orthio pseudo cyanines in which substituted or unsubstituted benzene ringsare fused on to the benzo thiazole'nucleus of theparent thio-iso or thiopseudo cyanine molecule in the 3 4 or the 5 6 position and dyes ofthistype containing simiemulsion containing a cyanine dye which contains anaphthothiazole nucleus and a quinoline nucleus.

2. A photographic gelatinosilver-halide emulsion containing a cya-ninedye which contains a naphthothiazole nucleus and a quinoline nucleus,the nitrogen atoms of the two nuclei being connected by a chainconsisting of an uneven number of carbon atoms.

3. A photographic gelatino-silver-halideemulsion containing a cyanidedye containing a quinoline nucleus and a naphthothiazole nucleus, thenitrogenatoms of which are-each linked to an alkyl group while one isalso linked to a suitable acid radical.

4. A photographic gelatino-silver-halideemulsion containing a cyaninedye containing a quinoline nucleus and a naphthothiazole nucleus, thenitrogen atoms of which are linked to dissimilar alkyl groups while oneis also linked to a suitable acid radical.

5. A photographic gelatino-silver-halideemulsion containing a cyaninedye containing a quinoline nucleus and .a naphthothiazole nucleus, thenitrogen atoms of which are each linked to an ethyl group while one isalso linked to an iodine atom.

G; A photographic gelatino-silvenhalide emulsion containing a cyaninedye of the thio-pseudo-cyanine series naphthothiazole nucleus.

containing a 7. A photographic gelatino-silver-halide emulsioncontaining a cyanine dye which contains a naphthothiazole nucleus and aquinoline nucleus, the nitrogen atoms of the two nuclei being connectedby a chain consisting of three carbon atoms.

8. A photographic gelatino-silver-halide empulsion containing aSA-benzo-thiopseudo-cyanine salt.

9. A photographic gelatinosilver-halideemulsion containing a 1 2dialkyl-benzothio-pseudo-cyanine salt.

10. A photographic gelatino-silver-halide emulsion containing a1-alkyl-2-alkyl-benzothio-pseudo-cyanine salt.

11. A photographic gelatino-silver-halide emulsion containing alz2-diethyl-3z4- be-nzo-thio-pseudo-cyanine salt.

12. A photographic gelatino-silver-halide emulsion containing a1-ethyl-2-methyl-3 :4- benzo-thio-pseudo-cyanine salt.

13. A photographic gelatino-silver-halide emulsion containing a 1:2dimethyl-3:4- benzo-thio-pseudo-cyanine salt.

14. A photographic gelatino-silver-halide emulsion containing a cyaninedye of the thio-iso-cyanine series containing a naphthothiazole nucleus.

15. A photographic gelatino-silVer-halide emulsion containing a cyaninedye which contains a naphthothiazole nucleus and a quinoline nucleus,the nitrogen atoms of the two nuclei being connected by achainconsisting of five carbon atoms.

16. A photographic gelatino-silVer-halide emulsion containing a3:4-benzo-thio-isocyanine salt.

17. A photographic gelation-silver-halide emulsion containing al:2-dialkyl-thio-isocyanine salt.

18. A photographic gelatino-silVer-halide emulsion containing a1-alkyl-2-alkyl-benzo thio-iso-cyanine salt.

19. A photographic gelatino-silver-halide emulsion containing alz2-diethyl-3z4- benzo-thio-iso-cyanine salt.

20. A photographic gelatino-silver-halide emulsion containing a1-ethyl2-methyl-3 4- benzo-thio-iso-cyanine salt.

21. A photographic gelatino-silver-halide emulsion containing a1-methyl2-ethyl-3': 4- benzo thio-iso-cyanine salt.

22. As a new product, a photographic film coated with agelatino-silver-halide emulsion containing a cyanine dye which containsa naphthothiazole nucleus and a quinoline nucleus.

Signed at Rochester, New York, this 5th day of March, 1980.

LESLIE G. S. BROOKER.

formula and insert ins tead Certificate of Correction Patent No.1,861,836. J une 7,1932.

LESLIE G. s. BROOKER.

It is hereby certified that error appears in the printed specificationof the abovenumbered patent requiring correction as follows: Page 2,lines 48 to 54, strike out the /S-1COHa page 3, line 79, ,for 5:6:5'z6read 5:6:5:6,' page 4, line 110, claim 3, for cyanide read ayam'ne; page5, line 8, claim 8, for empulsion read emulsion: line 38, claim 17, forgelation read gelatino andline 39, for 1 2-dialkyl-thio-isoread 1'Z-diaZkyZ-benzo-thio-iso-; and that the said Letters Patent should beread with these corrections therein that the same may conform to therecord of the case in the Patent Ofiice.

Signed and sealed this 16th day of August, A. D. 1932.

[m] i J. MOORE, Acting Uowwnissioner of Patents.

